I was given the Back to the Roots aquaponics fish tank as a present a while ago. I removed the 6 pot system it had and just filled the entire top with pumice. Then I seeded some water cress since the roots would be submerged on the bottom of the pumice bed. Here's a 115 day span from January 14th to March 8th.
I stopped taking pictures when I left the house for two weeks, but the water cress continued to get quite large.
The downfall of the system came, as often seems to be the case with aquaponic systems, with a pump problem I didn't notice. It had was drawing some air and no longer had enough pressure to fill the upper basin with water. After a few days of 85 degree weather the watercress got totally fried in the window. I just put a mint cuting in so we'll see how that works. The problem with growing most food crops in this aquaponics system is that you can never get enough light from just a window, you really need a grow light to get enough lux.
Watercress, or Nasturtium officinale, actually has its very own festival in Alresford, England:
Bet it gets real rowdy at night.